This proposal outlines studies of the visual system of the fruit-fly Drosophila. The proposed experiments concentrate on determining mechanisms of hereditary retinal degeneration in mutants. Retinal degeneration mutants will be studied singly and in genetic combination with mutants having visual excitation deficits. Analyses of these strains will also be used to determine photopigment properties, receptor function, excitation mechanisms and receptor input and integration into behavior. With Drosophila, one has unique genetic opportunities to manipulate the visual system, systematically eliminatng transduction or adaptation steps or systematically simplifying the retina in a strategy known as genetic dissection. Research on vision in Drosophila fits into an international literature on vision in flies integrated from photopigments to behavior. The work proposed here is designed in part to develop animal models for retinal degeneration pathology. The visual mutants are also used as manipulations in experiments addressed towards issues of current interest in excitation and neural processing. Extensive characterization will be undertaken on mutants which have been widely used in recent vision studies. Other experiments will concentrate on developing new model mutants which can be used to alter retinal function. The techniques used in this study involve optics, physiological recording and behavioral analyses which I have used successfully in previously published studies.